1. Field of the Invention
The present invention relates to a travelling vehicle system and a method of controlling the travelling of travelling vehicles in curved sections, and in particular relates to blocking in curved sections.
2. Description of the Related Art
In a system of travelling vehicles such as overhead travelling vehicles or automated guided vehicles, the travelling vehicles include obstacle sensors and avoid interference autonomously. Detecting a leading vehicle is difficult in a diverging section, a merging section, and the like, and therefore exclusion control is performed by a ground controller to limit the number of travelling vehicles travelling in a diverging section, a merging section, or the like at the same time to one vehicle (see, for example, WO 2009/142051A). However, this control is inefficient since the number of travelling vehicles that can pass through the diverging section or the merging section per unit time decreases. In view of this, consideration has been provided to eliminating the need for exclusion control by providing travelling vehicles with an obstacle sensor for curved travel (see, for example, JP 2011-165025A)
However, detecting a leading vehicle in a curved section with an obstacle sensor is not easy. Firstly, since the leading vehicle is travelling along a curve, the monitoring range spreads out like a fan. Secondly, when detecting reflected light from a leading vehicle, the direction of the reflected light changes because the direction of the leading vehicle changes as it travels along a curve. For this reason, the obstacle sensor for curved travel needs to be adjusted finely, and there are cases where the detection of a leading vehicle is delayed if there is deviation in the adjustment.